1. Field of the Invention
This invention relates to an ultrasonic welding/cutting machine which holds a sheet material such as film or unwoven fabric between a machining roller and a tool horn to which ultrasonic waves are transmitted, thereby welding or cutting the sheet material.
2. Description of the Related Art
Japanese patent publication No. 62-8296-B (1987) discloses an ultrasonic welding machine of the type described above. Japanese utility model publication No. 62-7465-B (1987) also discloses another ultrasonic welding machine of the above-described type. The welding machine disclosed in the former publication comprises a feeding mechanism for feeding a sheet material, a horn rotating mechanism for rotating a tool horn in response to a sheet feeding operation, a roller rotating mechanism for rotating a machining roller in response to the sheet feeding operation, and a moving mechanism for moving the tool horn and machining roller or an ultrasonic machining unit in a direction generally perpendicular to a direction in which the sheet material is fed. The sheet material, while being fed, is welded or cut by the tool horn and machining roller, so that a welded line or cut line, namely, a post-machining straight line extending in the same direction that the sheet material is fed is obtained. Furthermore, when the tool horn and machining roller are moved in the direction generally perpendicular to the direction in which the sheet material is fed, with the sheet material remaining stationary, a post-machining straight line extending in the direction generally perpendicular to the direction in which the sheet material is fed. In this construction, however, a curved line cannot be obtained when the sheet material has been welded or cut.
On the other hand, Japanese patent publication No. 6-297608-A (1994) discloses an ultrasonic welding machine in which the sheet material is machined curvilinearly so that a curved line is obtained. In the disclosed machine, the machining roll and the tool horn have respective special shapes in order that a required curved line may be obtained. However, the machining roller and the tool horn respectively having special shapes are expensive. Furthermore, since the shapes of the machining roller and the tool horn need to be changed depending upon the types of the curved lines, a large number of types of machining rollers and tool horns must be prepared. This increases the cost of the ultrasonic welding machine. Additionally, since the shapes of obtained curved lines are already determined by the prepared machining rollers and tool horns, a desired post-machining shape cannot sometimes be obtained.